DR Samir Messaoudi
In recent years, increased attention has been paid to Ionic Liquids. The gain in interest for such a class of compounds stems from the combination of these unique characteristics among, low vapor pressure, non-flammability and excellent chemical and thermal properties. Their high electrochemical stability has made them as good candidates as electrolyte for lithium ion batteries to improve the energy density by integrating more oxidizing electrode materials (> 4.5 V vs Li+ / Li) and to inhibit the growth of the lithium dendrite to the lithium negative electrode during recharging of the battery. The thesis project is based on the results obtained on the grafting of small imidazolium ion molecules on silica nanoparticles. The work will consist in a first step to validate the use of this type of compounds as a multi-technological monolithic electrolyte by their integration in model systems. In a second step, these results will be used in order to (i) develop novel silica-based hybrid electrolytes incorporating lithium complexing / chelating fragments and (ii) to understand the mobility of ions in such compounds.
Lu, B.; Miao, Y.; Vigneron, P.; Chagnault, V.; Grand, E.; Wadouachi, A.; Postel, D.; Pezron, I.; Egles, C.; Vayssade, M.
Sugar-based surfactants present surface-active properties and relatively low cytotoxicity. They are often considered as safe alternatives to currently used surfactants in cosmetic industries. In this study, four sugar-based surfactants, each with an eight carbon alkyl chain bound to a glucose or a maltose headgroup through an amide linkage, were synthesized and compared to two standard surfactants. The cytotoxic and irritant effects of surfactants were evaluated using two biologically relevant models: 3D dermal model (mouse fibroblasts embedded in collagen gel) and reconstituted human epidermis (RHE, multi-layered human keratinocytes). Results show that three synthesized surfactants possess lower cytotoxicity compared to standard surfactants as demonstrated in the 3D dermal model. Moreover, the IC50s of surfactants against the 3D dermal model are higher than IC50s obtained with the 2D dermal model (monolayer mouse fibroblasts). Both synthesized and standard surfactants show no irritant effects after 48 h of topical application on RHE. Throughout the study, we demonstrate the difficulty to link the physico-chemical properties of surfactants and their cytotoxicity in complex models. More importantly, our data suggest that, prior to in vivo tests, a complete understanding of surfactant cytotoxicity or irritancy potential requires a combination of cellular and tissue models.
Herreros-López, A.; Carini, M.; Da Ros, T.; Carofiglio, T.; Marega, C.; La Parola, V.; Rapozzi, V.; Xodo, L. E.; Alshatwi, A. A.; Hadad, C.; Prato, M.
The covalent grafting of two amino-fullerene C60 derivatives (C60-LC-NH2 and C60-SC-NH2, LC = long chain and SC = short chain) onto the surface of TEMPO oxidized nanocrystalline cellulose (NCC-COOH) has been reported for the first time. These hybrids (NCC-LC-C60 and NCC-SC-C60) form stable colloidal suspensions at concentrations up to 0.5 mg/mL and act as effective photosensitizers for singlet oxygen production as demonstrated by the oxidation of L-methionine-methyl ester to the corresponding sulphoxide. Using the same approach, in a one-pot reaction both a fluorescent target molecule (FITC-LC-NH2) and the C60-LC-NH2 derivative have been successfully attached covalently onto the NCC-COOH surface. These hybrids, which showed no cytotoxicity on MCF-7 human breast cancer cells could be good candidates in photodynamic cancer therapy.
Cavoue, T.; Bounou Abassi, H.; Vayssade, M.; Nguyen Van Nhien, A.; Kang, I. K.; Kwon, G. W.; Pourceau, G.; Dubot, P.; Abbad Andaloussi, S.; Versace, D. L.
Nosocomial infections are often induced by the presence of pathogenic organisms on the surface of medical devices or hospital equipment. Chemical modifications of the surface are recognized as efficient strategies to prevent bacterial adhesion but they may have a negative impact on the material's interaction with living tissues. Here we have developed a photoactivated method for the modification of titanium substrates. A photoinduced technique employing a grafting-onto process has been successfully performed to covalently anchor an imidazolium-derivative siloxane onto titanium surfaces. Imidazolium surfaces showed higher bacteria-repellency performances than native titanium substrates, achieving more than 98% anti-adhesion efficiency against Escherichia coli after 24 h of incubation. In addition, these surfaces allowed for the adhesion and viability of osteoblasts cells without evidence of cytotoxicity.
Ramsay, A.; Fliniaux, O.; Quéro, A.; Molinié, R.; Demailly, H.; Hano, C.; Paetz, C.; Roscher, A.; Grand, E.; Kovensky, J.; Schneider, B.; Mesnard, F.
The main flax lignan, secoisolariciresinol diglucoside, is stored in a macromolecule containing other ester-bound phenolic compounds. In this study, NMR and HPLC-UV analyses were performed on flaxseeds harvested at different developmental stages to identify and quantify the main phenolic compounds produced during seed development. Extraction was carried out with or without alkaline hydrolysis to determine if these molecules accumulate in the lignan macromolecule and/or in a free form. Monolignol glucosides accumulate in a free form up to 9.85 mg/g dry matter at the early developmental stages. Hydroxycinnamic acid glucosides and flavonoid accumulate (up to 3.18 and 4.07 mg/g dry matter, respectively) in the later developmental stages and are ester-bound in the lignan macromolecule. Secosiolariciresinol diglucoside accumulates (up to 28.65 mg/g dry matter) in the later developmental stages in both forms, mainly ester-bound in the lignan macromolecule and slightly in a free form.
Lu, H.; Drelich, A.; Omri, M.; Pezron, I.; Wadouachi, A.; Pourceau, G.
Large quantities (>3 g) of a new series of alkyl uronates were synthesized in two steps from commercial methyl hexopyranosides. Firstly, several tens of grams of free methyl α-d-glucopyranoside were selectively and quantitatively oxidized into corresponding sodium uronate using 2,2,6,6-tetramethyl-1-piperidinyloxy free radical (TEMPO)-catalyzed oxidation. Hydrophobic chains of different length were then introduced by acid-mediated esterification with fatty alcohols (ethyl to lauryl alcohol) leading to the desired alkyl glucuronates with moderate to good yields (49%–72%). The methodology was successfully applied to methyl α-d-mannopyranoside and methyl β-d-galactopyranoside. Physicochemical properties, such as critical micelle concentration (CMC), equilibrium surface tension at CMC (γcmc), solubility, and Krafft temperature were measured, and the effect of structural modifications on surface active properties and micelle formation was discussed.
Flasque, M.; Nhien, A. N. V.; Moia, D.; Barnes, P. R. F.; Sauvage, F.
Solid electrolyte interphase (SEI) layers form on sensitized-TiO2 photoanodes and platinum counter electrodes when dye-sensitized solar cells (DSSCs) are subjected to an accelerated aging protocol (e.g., heating at 85 °C in the dark for 500 h). To understand how this impacts device operation, we conducted an electrochemical impedance spectroscopy study and found that the SEI induces an additional electron-transfer process from the TiO2 to the electrolyte. This is materialized by the onset of a new charge-transfer semicircle at higher frequencies, predominantly visible under bias voltages similar to and greater than the open-circuit voltage. Our results emphasize the detrimental role of SEI formation on device performance and lifetime. Additionally, nanosecond transient absorption spectroscopy showed that SEI formation reduced the rate of oxidized dye regeneration. We also found that a proportion of the photogenerated holes on the dyes were transferred to the SEI itself. A prolonged aging duration led to the electrode’s mesoporosity network being entirely clogged by the SEI, thus impeding efficient transport of the electrolyte redox couple and being responsible for a further decline in photovoltaic performances.
Bacterial lectins are nonenzymic sugar-binding proteins involved in the formation of biofilms and the onset of virulence. The weakness of individual sugar-lectin interactions is compensated by the potentially large no. of simultaneous copies of such contacts, resulting in high overall sugar-lectin affinities and marked specificities. Therapeutic compds. functionalized with sugar residues can compete with the host glycans for binding to lectins only if they are able to take advantage of this multivalent binding mechanism. Glycopeptide dendrimers, featuring treelike topologies with sugar moieties at their leaves, have already shown great promise in this regard. However, optimizing the dendrimers' amino acid sequence is necessary to match the dynamics of the lectin active sites with that of the multivalent ligands. This work combines long-time-scale coarse-grained simulations of dendrimers and lectins with a reasoned exploration of the dendrimer sequence space in an attempt to suggest sequences that could maximize multivalent binding to the galactose-specific bacterial lectin LecA. These candidates are validated by simulations of mixed dendrimer/lectin solns., and the effects of the dendrimers on lectin dynamics are discussed. This approach is an attractive first step in the conception of therapeutic compds. based on the dendrimer scaffold and contributes to the understanding of the various classes of multivalency that underpin the ubiquitous "sugar code".